我打电话时没有调用DataReceivedHandler？

Question

我想注册事件，以便在有电话的时候随时调用它如何实现

   private void SpecialCallerID()
        {
            serialPort = new SerialPort(ComPort);

            serialPort.BaudRate = 9600;
            serialPort.Parity = Parity.None;
            serialPort.StopBits = StopBits.One;
            serialPort.DataBits = 8;
            serialPort.Handshake = Handshake.None;
            serialPort.ReadTimeout = 100;
            serialPort.DtrEnable = true;  // Data-terminal-ready
            serialPort.Open();
            //serialPort.RtsEnable = true;    // Request-to-send
            serialPort.DataReceived += new SerialDataReceivedEventHandler(this.serialPortNEW_DataReceived);
          //  mySerialPort.Close();

        }

        private void serialPortNEW_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) {

            SerialPort sp = (SerialPort)sender;
            string indata = sp.ReadExisting();
            string[] strFirstStep = Regex.Split(indata, "\r\nNMBR =");
            string[] strLastStep = Regex.Split(strFirstStep[1], "\r\n");
            string FinalValue = strLastStep[0];

            custNUmber = int.Parse(FinalValue);
}